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INFM 603 – Information Technology and Organizational Context Lecture 8 Entity Relationship Diagrams.

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Presentation on theme: "INFM 603 – Information Technology and Organizational Context Lecture 8 Entity Relationship Diagrams."— Presentation transcript:

1 INFM 603 – Information Technology and Organizational Context Lecture 8 Entity Relationship Diagrams

2 2 Entity “An entity is a business object that represents a group, or category of data.” 1 Do we know a similar concept? 1) Stephens, R.K. and Plew. R.R., Database Design. SAMS, Indianapolis, IN.

3 3 Attribute “An attribute is a sub-group of information within an entity.” 1 Do we know a similar concept? 1) Stephens, R.K. and Plew. R.R., Database Design. SAMS, Indianapolis, IN.

4 4 Entity Relationship Models Mandatory Relationships Optional Relationships Many-to-Many Relationships One-to-Many Relationships One-to-One Relationships Recursive Relationships

5 5 Mandatory, Many-to-Many INSTRUCTORSTUDENTINSTRUCTORSTUDENT

6 6 Optional, Many-to-Many DEPARTMENTSTUDENTDEPARTMENTSTUDENT

7 7 Optional/Mandatory, Many-to-Many INSTRUCTORSKILLINSTRUCTORSKILL

8 8 Optional/Mandatory, One-to-Many PRODUCTVENDORPRODUCTVENDOR

9 9 Mandatory, One-to-One AUTOMOBILEENGINEAUTOMOBILEENGINE

10 10 Recursive EMPLOYEE supervises is supervised by

11 11 Resolving Many-to-Many Relationships Many-to-many relationships should be avoided. We can resolve a many-to-many relationship by dividing it into two one-to- many relationships.

12 12 Resolving Many-to-Many Relationships SALES ORDERSINV. ITEMSSALES ORDERSINV. ITEMSORDER ITEMS

13 13 Example (ER Diagram) SALES ORDERS INV. ITEMSORDER ITEMS CLERKSCUSTOMERS


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